PHYSICAL REVIEW LETTERS 123, 052001 (2019) Editors' Suggestion Featured in Physics Observation of Light-by-Light Scattering in Ultraperipheral Pb + Pb Collisions with the ATLAS Detector G. Aad et al.* (ATLAS Collaboration) (Received 11 April 2019; published 31 July 2019) This Letter describes the observation of the light-by-light scattering process, γγ → γγ, in Pb þ Pb pffiffiffiffiffiffiffiffi collisions at sNN ¼ 5.02 TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73 nb−1 , collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy EγT > 3 GeV and pseudorapidity jηγ j < 2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12  3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78  13ðstatÞ  7ðsystÞ  3ðlumiÞ nb. DOI: 10.1103/PhysRevLett.123.052001 Light-by-light scattering, γγ → γγ, is a quantum- collision (UPC) events. In general, this allows us to study mechanical process that is forbidden in the classical theory processes involving nuclear photoexcitation, photoproduc- of electrodynamics [1,2]. In the standard model (SM), the tion of hadrons, and two-photon interactions [15,16]. The γγ → γγ reaction proceeds at one-loop level at order α4EM EM fields produced by the colliding Pb nuclei can be (where αEM is the fine-structure constant) via virtual box described as a beam of quasireal photons with a small diagrams involving electrically charged fermions (leptons virtuality of Q2 < 1=R2 , where R is the radius of the charge and quarks) or W  bosons. However, in various extensions distribution, and so, Q2 < 10−3 GeV2 [17,18]. The cross of the SM, extra contributions are possible, making the section for the elastic reaction Pb þ PbðγγÞ → Pb þ Pbγγ measurement of γγ → γγ scattering sensitive to new phys- can then be calculated by convolving the appropriate ics. Relevant examples are magnetic monopoles [3], photon flux with the elementary cross section for the vectorlike fermions [4], and axionlike particles [5,6]. process γγ → γγ. Since the photon flux associated with The light-by-light cross section is also sensitive to the each nucleus scales with the square of the number of effect of possible non-SM operators in an effective field protons, the cross section is strongly enhanced relative to theory [7–9]. Light-by-light scattering graphs with electron proton-proton (pp) collisions. loops also contribute to the anomalous magnetic moment of The γγ → γγ reaction has also been measured in photon the electron and muon [10,11]. scattering in the Coulomb field of a nucleus (Delbrück Strong evidence for this process in relativistic heavy-ion scattering) [19–22] and in the photon-splitting process [23]. (Pb þ Pb) collisions at the Large Hadron Collider (LHC) A related process, in which initial photons fuse to form has been reported by the ATLAS [12] and CMS [13] a pseudoscalar meson that subsequently decays into collaborations with observed significances of 4.4 and 4.1 a pair of photons, has been studied at electron-positron standard deviations, respectively. Exclusive light-by-light colliders [24–27]. scattering can occur in these collisions at impact parameters The previous ATLAS and CMS measurements were larger than about twice the radius of the ions, as demon- based on the Pb þ Pb dataset of 0.4 nb−1 recorded in 2015 strated for the first time in Ref. [14]. The strong interaction at a nucleon-nucleon (NN) center-of-mass energy of pffiffiffiffiffiffiffiffi becomes less significant and the electromagnetic (EM) sNN ¼ 5.02 TeV [12,13]. The present Letter describes interaction becomes more important in these ultraperipheral a new measurement exploiting 1.73 nb−1 of Pb þ Pb pffiffiffiffiffiffiffiffi collisions at sNN ¼ 5.02 TeV, recorded in November * Full author list given at the end of the article. 2018 with the ATLAS detector at the LHC. The analysis follows the approach originally proposed in Ref. [14], Published by the American Physical Society under the terms of which was the basis of the initial ATLAS measurement. the Creative Commons Attribution 4.0 International license. The ATLAS detector [28] is a multipurpose particle Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, detector that covers nearly the entire solid angle around the and DOI. Funded by SCOAP3. interaction point (IP) [29]. It consists of an inner detector 0031-9007=19=123(5)=052001(21) 052001-1 © 2019 CERN, for the ATLAS Collaboration PHYSICAL REVIEW LETTERS 123, 052001 (2019) (ID) for charged-particle tracking in the pseudorapidity the absolute normalization of this background is deter- region jηj < 2.5, EM and hadronic calorimeters that pro- mined using a control region in the data, as explained later. vide energy measurements up to jηj ¼ 4.9, and a muon The γγ → eþ e− process is a potential background when spectrometer that covers jηj < 2.7. Forward calorimeters both leptons are reconstructed as photons but is also used (FCAL) cover the range of 3.2 < jηj < 4.9. The zero- for calibration studies in the analysis. The process was degree calorimeters (ZDC), located along the beam axis at modeled with the STARLIGHT 2.0 generator. Its production 140 m from the IP on both sides, detect neutral particles, cross section is computed by combining the PbþPb photon including neutrons emitted from the nucleus. flux with the leading-order formula for γγ →eþ e−. Two- The final-state signature of interest is the exclusive photon production of quark-antiquark pairs, with their production of two photons, PbþPbðγγÞ → PbðÞ þPbðÞ γγ, subsequent decay into multiple hadrons, was modeled where the diphoton final state is measured in the central using HERWIG++ 2.7.1 [39], where the initial photon fluxes detector, and the incoming Pb ions survive the EM inter- from pp collisions are implemented. The sample was then action, with a possible EM excitation [30], denoted by ð Þ. normalized to cover the differences in the photon fluxes Hence, the final state consists of two low-energy photons and between Pb þ Pb and pp collisions. All simulated events no further activity in the detector and, in particular, no make use of a detector simulation [40] based on GEANT4 reconstructed charged-particle tracks originating from the IP. [41] and are reconstructed with the standard ATLAS A two-level trigger system was used to select events reconstruction software. online [31]. It consists of a level-1 trigger implemented Photons are reconstructed from EM clusters in the using a combination of custom electronics and program- calorimeter [42] and tracking information provided by mable logic, and a software-based high-level trigger (HLT). the ID, which allows us to identify photon conversions Candidate diphoton events were recorded using a dedicated [43]. An energy calibration specifically optimized for trigger for events with moderate activity in the calorimeter photons [44] is applied to account for energy loss before but little additional activity in the detector. At level 1, a the calorimeter and both lateral and longitudinal shower logical OR of two conditions was required: at least one EM leakage. Photons in MC samples are corrected [43] for cluster with ET > 1 GeV in coincidence with a total ET of known mismodeling of quantities that describe the proper- 4–200 GeV measured in the calorimeter, or at least two EM ties (“shapes”) of the associated EM showers. clusters with ET > 1 GeV with total ET measured in the The photon particle identification (PID) in this analysis is calorimeter below 50 GeV. The upper bound on the total ET based on a selection of these shower-shape variables, was optimized to be fully efficient for signal events optimized for the signal events. Only photons with ET > while allowing the rejection of events from nonperipheral 3 GeV and jηj < 2.37, excluding the calorimeter transition Pb þ Pb collisions. At the HLT, the total FCAL ET on each region 1.37 < jηj < 1.52, are considered. This allows for side of the IP was required to be consistent with noise good separation between prompt photons and fake signatures (FCAL veto), and the number of hits in the pixel detector due to calorimeter noise, cosmic-ray muons, or nonprompt (part of the ID) was required to be, at most, 15. photons originating from the decay of neutral hadrons. The Simulated γγ → γγ signal events were generated using photon PID is based on a neural network trained on back- the SUPERCHIC 3.0 Monte Carlo (MC) generator [32]. This ground photons extracted from data and on photons from the program takes into account box diagrams with charged signal MC sample. The selection of background photons leptons, quarks, and W  bosons. An alternative signal follows the procedure established in Ref. [12]. sample was generated using calculations from Ref. [33]. Selected events are required to have exactly two photons These calculations were then folded with the Pb þ Pb satisfying the above selection criteria, with a diphoton photon flux taken from the STARLIGHT 2.0 MC generator invariant mass (mγγ ) greater than 6 GeV. In order to [34]. The theoretical uncertainty of the cross section is suppress the γγ → eþ e− background, events are rejected mainly due to the limited knowledge of the nuclear form if they have a charged-particle track with pT > 100 MeV, factors and initial photon fluxes. This is extensively studied jηj < 2.5, and at least six hits in the pixel and microstrip in Refs. [13,35], and the relevant uncertainty is estimated to detectors, including at least one pixel hit. To further be 10% within the fiducial phase space of the measurement. suppress γγ → eþ e− events with poorly reconstructed Higher-order corrections, which are not included in the charged-particle tracks, candidate events are required to calculations, are also part of the theoretical uncertainty and have no “pixel tracks” matched to a photon candidate amount to 1%–3% in the fiducial phase space [36,37]. within jΔηj < 0.5. Pixel tracks are reconstructed using The exclusive diphoton final state can also be produced information from the pixel detector only. They are required via the strong interaction through a quark loop in the to have pT > 50 MeV, jηj < 2.5, and at least three hits in exchange of two gluons in a color-singlet state. This the pixel detector. According to the MC simulation, these central exclusive production (CEP) process, gg → γγ, requirements reduce the fake photon background from the was also modeled using SUPERCHIC 3.0. This process dielectron final state by a factor of 104 , while being 93% has a large theoretical uncertainty, of Oð100%Þ [38]; hence efficient for γγ → γγ signal events. 052001-2 PHYSICAL REVIEW LETTERS 123, 052001 (2019) 1.05 ATLAS 1 ATLAS ATLAS Photon reconstruction efficiency 1 1 Level-1 trigger efficiency 0.9 Photon PID efficiency 0.95 0.8 0.8 0.9 0.6 0.7 0.85 Pb+Pb sNN=5.02 TeV 0.6 0.8 0.4 -1 Data 2018, 1.7 nb Pb+Pb sNN=5.02 TeV Fit to data 0.5 eeγ (hard-brem) selection 0.75 Pb+Pb sNN=5.02 TeV 0.2 -1 -1 Stat Data 2018, 1.7 nb Data 2018, 1.7 nb FSR photons 0.4 0.7 Stat ⊕ syst γ γ →ee MC γ γ → γ γ MC 0 0.65 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 18 20 0 5 10 15 20 25 cluster1 cluster2 e ET +E T [GeV] ET,1 - ptrk2 [GeV] Photon ET [GeV] T (a) (b) (c) FIG. 1. (a) Measured level-1 trigger efficiency as a function of the reconstructed transverse energy in γγ → eþ e− events, (b) photon reconstruction efficiency as a function of the photon ET (approximated with EeT;1 − ptrk2 T , where trk2 denotes the track of the second leading electron), and (c) photon particle-identification efficiency as a function of the photon ET . To reduce other fake-photon backgrounds, such as Because of the high hit-reconstruction efficiency and cosmic-ray muons, the transverse momentum of the dipho- relatively low conversion probability of signal photons in ton system (pγγ T ) is required to be below 1 GeV for mγγ < the pixel detector, the inefficiency of the pixel veto 12 GeV and below 2 GeV for mγγ > 12 GeV. To reduce requirement at the trigger level is found to be negligible. prompt-photon background from CEP gg → γγ reactions, The photon reconstruction efficiency is extracted from an additional requirement on the reduced acoplanarity, data using γγ → eþ e− events, where one of the electrons Aϕ ¼ ð1 − jΔϕγγ j=πÞ < 0.01, is used, which is expected to emits a hard bremsstrahlung photon due to interaction with have ð86  1Þ% selection efficiency for the signal. This the material of the detector. The analysis is performed for efficiency is estimated using simulated signal events, and events with exactly one identified electron and exactly two the uncertainty is due to modeling of the photon angular reconstructed charged-particle tracks, and a tag-and-probe resolution in simulation. The above requirements define the method is used as described in Ref. [12]. The resulting fiducial region for the signal measurement. photon reconstruction efficiency is shown in Fig. 1(b). It Exclusive dielectron pairs from the reaction PbþPbðγγÞ → rises from about 60% at ET ¼ 2.5 GeV to 90% at ET ¼ PbðÞ þPbðÞ eþ e− are used for various aspects of the analysis, 6 GeV and is used to derive simulation-to-data correction in particular, to validate the EM calorimeter energy scale and factors. resolution [44]. To select γγ → eþ e− candidates, events are High-pT exclusive dilepton production (γγ → lþ l− , required to pass the same trigger as for the diphoton selection. where l ¼ e, μ) with final-state radiation (FSR) is used Each electron is reconstructed from an EM energy cluster in to measure the photon PID efficiency, defined as the the calorimeter matched to a track in the ID [45]. The γγ → probability for a reconstructed photon to satisfy the eþ e− events are selected by requiring exactly two oppositely identification criteria. Events with exactly two oppositely charged electrons, no further charged-particle tracks coming charged tracks with pT > 0.5 GeV are selected from UPC from the interaction region, and dielectron reduced acopla- triggered events. In addition, a requirement to reconstruct a narity, Aϕ < 0.01. The observed γγ → eþ e− event yield in photon candidate with ET > 2.5 GeV and jηj < 1.37 or data is compatible with that expected from simulation. 1.52 < jηj < 2.37 is imposed. A photon candidate is The level-1 trigger efficiency is estimated with γγ → required to be separated from each track by fulfilling ΔR > eþ e− events passing an independent trigger. The level-1 0.3 [29] to avoid leakage between the photon and the trigger efficiency as a function of the electron EM cluster electron clusters. The FSR event candidates are required to transverse energy sum, Ecluster1 T þ Ecluster2 T , reaches 60% at have pllγ T < 1 GeV requirement, where pT llγ is the trans- 5 GeV and 75% at 6 GeV, with the fully efficient plateau verse momentum of the three-body system consisting of the reached at around 10 GeV, as shown in Fig. 1(a). The two tracks and the photon candidate. Figure 1(c) shows the measured efficiency is parametrized and used to correct photon PID efficiency as a function of reconstructed photon the trigger response in the simulation. To test the stability of ET , where the measurement from data is compared with the results, the analysis is repeated using tighter or looser the one extracted from the signal MC sample. Based on dielectron event selection criteria, and the resulting these studies, MC events are corrected using photon ET - differences are taken as a systematic uncertainty. The dependent simulation-to-data correction factors. The sys- FCAL veto efficiency is estimated using γγ → eþ e− events tematic uncertainty on the photon reconstruction and PID selected with a dedicated control trigger without involving efficiencies is estimated by parametrizing the correction the FCAL requirement. It is estimated to be ð99.1  0.6Þ%. factors as a function of the photon η instead of the photon ET . 052001-3 PHYSICAL REVIEW LETTERS 123, 052001 (2019) 50 18 ATLAS ATLAS 25 ATLAS 45 16 Pb+Pb sNN = 5.02 TeV Pb+Pb sNN = 5.02 TeV Pb+Pb sNN = 5.02 TeV 40 14 20 35 Data 2018, 1.7 nb-1 Data 2018, 1.7 nb-1 Data 2018, 1.7 nb-1 Events / 0.2 GeV Events / 0.005 12 Events / GeV 30 Signal (γ γ → γ γ ) Signal (γ γ → γ γ ) Signal (γ γ → γ γ ) CEP gg → γ γ 10 CEP gg → γ γ 15 CEP gg → γ γ 25 γ γ → ee γ γ → ee γ γ → ee 8 20 Sys. unc. Sys. unc. Sys. unc. 10 6 15 10 4 5 5 2 0 0 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 5 10 15 20 25 30 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Aφ γγ m γ γ [GeV] pT [GeV] (a) (b) (c) FIG. 2. (a) The diphoton Aϕ distribution for events satisfying the signal selection, but before the Aϕ < 0.01 requirement. (b) Diphoton invariant mass and (c) diphoton transverse momentum for events satisfying the signal selection. Data (points) are compared with the sum of signal and background expectations (histograms). Systematic uncertainties of the signal and background processes, excluding that of the luminosity, are shown as shaded bands. The two electrons exhibit balanced transverse momen- exhibit a significantly broader Aϕ distribution than the þ − tum with an unbalance, jpeT − peT j, expected to be below γγ → γγ process. In the CEP process gluons recoil against 30 MeV. This is much smaller than the EM calorimeter the Pb nucleus which then dissociates. The shape of the Aϕ energy resolution, which, thus, can be measured by the distribution for γγ → eþ e− events is mainly due to the difference Ecluster1 T − Ecluster2 T . Below 10 GeV electron ET , curvature of the trajectory of the electrons in the detector the relative energy resolution is found to be between 8% magnetic field before they emit hard photons in their and 10% and is well reproduced by the MC simulation. The interactions with the ID material. EM energy scale is validated using the ratio of the electron The estimated uncertainty in the CEP gg → γγ back- cluster EeT to the electron track ptrk T . ground takes into account the statistical uncertainty of the The γγ → eþ e− process can be a source of fake diphoton number of events in the Aϕ > 0.01 control region (17%) as events, since misidentification of electrons as photons can well as experimental and modeling uncertainties. It is found occur when the electron track is not reconstructed or the that all experimental uncertainties have negligible impact electron emits a hard bremsstrahlung photon. The γγ → on the normalization of the CEP gg → γγ background. The eþ e− yield in the signal region is evaluated using a data- impact of the MC modeling of the Aϕ shape is estimated driven method. Two control regions (CRs) are defined with using an alternative SUPERCHIC MC sample with no exactly two photons passing the signal selection but also absorptive effects [46]. These effects reflect the absence requiring one or two associated pixel tracks. The event of secondary particle emissions, which can take place in yield observed in these two CRs is extrapolated to the addition to the gg → γγ process. After applying the data- signal region using the probability to miss the electron pixel driven normalization procedure, this leads to a 25% change track if the electron track is not reconstructed (pemistag ). It is in the CEP background yield in the signal region, which is measured in a region with exactly one charged-particle taken as a systematic uncertainty. An additional check is track and two photons with Aϕ < 0.01. In order to verify done by varying the gluon parton distribution function the stability of the pemistag evaluation method, the Aϕ (PDF). The differences between the MMHT 2014 [47], CT14 [48], and NNPDF3.1 [49] PDF sets have negligible requirement is dropped and the difference with the nominal impact on the shape of the CEP diphoton Aϕ distribution. selection is taken as a systematic uncertainty. This leads to The background due to the CEP process in the signal region pemistag ¼ ð47  9Þ%. The number of γγ → eþ e− events in is estimated to be 4  1 events. In addition, the energy the signal region is estimated to be 7  1ðstatÞ  3ðsystÞ, deposition in the ZDC, which is sensitive to dissociation of where the uncertainty accounts for the CR statistical Pb nuclei, is studied for events before the Aϕ selection is uncertainty, the pemistag uncertainty, and the difference found imposed. Good agreement is observed between the nor- between the two CRs. malized CEP expectation from MC simulation and the The Aϕ < 0.01 requirement significantly reduces the observed events with a signal corresponding to at least one CEP gg → γγ background. Its remaining contribution is neutron in the ZDC. evaluated from a control region defined by applying the The background contribution from γγ → qq̄ production same selection as for the signal region, but inverting the Aϕ is estimated using MC simulation based on HERWIG++ and requirement to Aϕ > 0.01 [see Fig. 2(a)], and correcting the is found to be negligible. Exclusive two-meson production measured event yield for the expected signal and γγ → can be a potential source of background for light-by-light eþ e− contributions. The CEP and γγ → eþ e− processes scattering events, mainly due to their similar back-to-back 052001-4 PHYSICAL REVIEW LETTERS 123, 052001 (2019) R topology. Mesons can fake photons either by their inter- the number of background events, Ldt ¼ 1.730.07 nb−1 mediate decay into photons (neutral mesons: π 0 , η, η0 ) or by is the integrated luminosity of the data sample, and C is an misreconstructed charged-particle tracks (charged mesons: overall correction factor that accounts for efficiencies for example π þ , π − states). Estimates for such contributions and resolution effects. The C factor is defined as the ratio are reported in Refs. [14,50–53] and these contributions are of the number of selected MC signal events passing the considered to be negligible in the signal region. selection and after applying data/MC correction factors to The background from other fake diphoton events the number of generated MC signal events satisfying the (mainly those induced by cosmic-ray muons) is estimated fiducial requirements. It is found to be C ¼ 0.350  0.024. using a control region with at least one track reconstructed The uncertainty in C is estimated by varying the data/MC in the muon system and further studied using the recon- correction factors within their uncertainties, as well as structed photon-cluster time distribution. After imposing using an alternative signal MC sample based on calcula- the pγγT requirements, this background is found to be tions from Ref. [33]. The probability of additional inelastic negligible. Background from the γγ → eþ e− γγ reaction interactions in the same bunch crossing is estimated to be is evaluated using the MADGRAPH5_AMC@NLO MC gener- 0.3% and has negligible impact on the signal efficiency. ator [54] and the Pb þ Pb photon flux from STARLIGHT. The overall uncertainty is dominated by uncertainties in the This contribution is estimated to be below 1% of the photon reconstruction efficiency (4%) and the trigger expected signal and, therefore, has negligible impact on the efficiency (2%). The uncertainty of the integrated lumi- results. The contribution from bottomonia production (for nosity is derived, following a methodology similar to that example, γγ → ηb → γγ or γPb → ϒ → γηb → 3γ) is cal- detailed in Ref. [60], from a calibration of the luminosity culated using parameters from Refs. [55,56] and considered scale using x-y beam-separation scans performed in to be negligible. The contribution from UPC events where November 2018. both nuclei emit a bremsstrahlung photon is estimated The measured fiducial cross section is using calculations from Ref. [57]. The cross section for 78  13ðstatÞ  7ðsystÞ  3ðlumiÞ nb, which can be com- single-bremsstrahlung photon production from a Pb ion in pared with the predicted values of 45  5 nb from the fiducial region of the measurement is calculated to be Ref. [14], 51  5 nb from Ref. [33], and 50  5 nb from below 10−4 pb so that the coincidence of two such SUPERCHIC 3.0 MC simulation [32]. The experiment- occurrences is considered to be negligible. to-prediction ratios are 1.73  0.40, 1.53  0.33, and After applying the signal selection, 59 events are 1.56  0.33, respectively. observed in the data where 30  4ðsystÞ signal events In summary, this Letter reports the observation of light- and 121ðstatÞ3ðsystÞ background events are expected. by-light scattering in quasireal photon interactions from pffiffiffiffiffiffiffiffi The probability that the data are compatible with the ultraperipheral Pb þ Pb collisions at sNN ¼ 5.02 TeV background-only hypothesis was evaluated in a narrower recorded in 2018 by the ATLAS experiment. After applying 0 < Aϕ < 0.005 range which, in studies using simulated all selection criteria, 59 data events are observed in data, was found to be most sensitive. In this region, 42 the signal region, while 12  3 background events are events are observed in the data where 25  3ðsystÞ signal expected. The dominant background processes, i.e., CEP events and 6  1ðstatÞ  2ðsystÞ background events are gg → γγ, γγ → eþ e− as well as other fake-photon back- expected. The data excess is quantified by calculating the grounds, are estimated from data. The statistical signifi- background-only p value using a profile likelihood-ratio cance against the background-only hypothesis is found to test statistic [58], resulting in an observed (expected) be 8.2 standard deviations. statistical significance of 8.2 (6.2) standard deviations. We thank CERN for the very successful operation of the Photon kinematic distributions for events satisfying all LHC, as well as the support staff from our institutions selection criteria are shown in Figs. 2(b)–2(c). A further without whom ATLAS could not be operated efficiently. cross check of energy deposits in the ZDC for events in the We acknowledge the support of ANPCyT, Argentina; signal region is performed. The activity in the ZDC agrees YerPhI, Armenia; ARC, Australia; BMWFW and FWF, with the signal-plus-background expectation. The analysis Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and is also repeated with a lower minimum photon ET require- FAPESP, Brazil; NSERC, NRC, and CFI, Canada; CERN; ment of 2.5 GeV, yielding more signal events but also an CONICYT, Chile; CAS, MOST, and NSFC, China; increased relative background contribution. Consistent COLCIENCIAS, Colombia; MSMT CR, MPO CR, and results were found using this relaxed signal selection. VSC CR, Czech Republic; DNRF and DNSRC, Denmark; The cross section for the γγ → γγ process is measured in IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, a fiducial phase space, defined by a set of requirements on Georgia; BMBF, HGF, and MPG, Germany; GSRT, the diphoton final state, reflecting the selection at Greece; RGC, Hong Kong SAR, China; ISF and reconstruction level [59]. Experimentally, the fiducial R Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, cross section is given by σ fid ¼ðN data −N bkg Þ=ðC× LdtÞ, Japan; CNRST, Morocco; NWO, Netherlands; RCN, where N data is the number of selected events in data, N bkg is Norway; MNiSW and NCN, Poland; FCT, Portugal; 052001-5 PHYSICAL REVIEW LETTERS 123, 052001 (2019) MNE/IFA, Romania; MES of Russia and NRC KI, Russian [11] F. Jegerlehner and A. Nyffeler, The Muon g-2, Phys. Rep. Federation; JINR; MESTD, Serbia; MSSR, Slovakia; 477, 1 (2009). ARRS and MIZŠ, Slovenia; DST/NRF, South Africa; [12] ATLAS Collaboration, Evidence for light-by-light scatter- MINECO, Spain; SRC and Wallenberg Foundation, ing in heavy-ion collisions with the ATLAS detector at the LHC, Nat. Phys. 13, 852 (2017). 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Chiu,176 M. V. Chizhov,79 K. Choi,65 A. R. Chomont,72a,72b S. Chouridou,162 Y. S. Chow,120 M. C. Chu,63a X. Chu,15a J. Chudoba,141 A. J. Chuinard,103 J. J. Chwastowski,84 L. Chytka,130 K. M. Ciesla,84 D. Cinca,47 V. Cindro,91 I. A. Cioară,27b A. Ciocio,18 F. Cirotto,69a,69b Z. H. Citron,180 M. Citterio,68a D. A. Ciubotaru,27b B. M. Ciungu,167 A. Clark,54 M. R. Clark,39 P. J. Clark,50 C. Clement,45a,45b Y. Coadou,101 M. Cobal,66a,66c A. Coccaro,55b J. Cochran,78 H. Cohen,161 A. E. C. Coimbra,36 L. Colasurdo,119 B. Cole,39 A. P. Colijn,120 J. Collot,58 P. Conde Muiño,140a,n E. Coniavitis,52 S. H. Connell,33b I. A. Connelly,57 S. Constantinescu,27b F. Conventi,69a,o A. M. Cooper-Sarkar,135 F. Cormier,175 K. J. R. Cormier,167 L. D. Corpe,94 M. Corradi,72a,72b E. E. Corrigan,96 F. Corriveau,103,p A. Cortes-Gonzalez,36 M. J. Costa,174 F. Costanza,5 D. Costanzo,149 G. Cowan,93 J. W. Cowley,32 J. Crane,100 K. Cranmer,124 S. J. Crawley,57 R. A. Creager,137 S. Crépé-Renaudin,58 F. Crescioli,136 M. Cristinziani,24 V. Croft,120 G. Crosetti,41b,41a A. Cueto,5 T. Cuhadar Donszelmann,149 A. R. Cukierman,153 S. Czekierda,84 P. Czodrowski,36 M. J. Da Cunha Sargedas De Sousa,60b J. V. Da Fonseca Pinto,80b C. Da Via,100 W. Dabrowski,83a T. Dado,28a S. Dahbi,35e T. Dai,105 C. Dallapiccola,102 M. Dam,40 G. D’amen,23b,23a V. D’Amico,74a,74b J. Damp,99 J. R. Dandoy,137 M. F. Daneri,30 N. P. Dang,181 N. D Dann,100 M. Danninger,175 V. Dao,36 G. Darbo,55b O. Dartsi,5 A. Dattagupta,131 T. Daubney,46 S. D’Auria,68a,68b W. Davey,24 C. David,46 T. Davidek,143 D. R. Davis,49 I. Dawson,149 K. De,8 R. De Asmundis,69a M. De Beurs,120 S. De Castro,23b,23a S. De Cecco,72a,72b N. De Groot,119 P. de Jong,120 H. De la Torre,106 A. De Maria,15c D. De Pedis,72a A. De Salvo,72a U. De Sanctis,73a,73b M. De Santis,73a,73b A. De Santo,156 K. De Vasconcelos Corga,101 J. B. De Vivie De Regie,132 C. Debenedetti,146 D. V. Dedovich,79 A. M. Deiana,42 M. Del Gaudio,41b,41a J. Del Peso,98 Y. Delabat Diaz,46 D. Delgove,132 F. Deliot,145,q C. M. Delitzsch,7 M. Della Pietra,69a,69b D. Della Volpe,54 A. Dell’Acqua,36 L. Dell’Asta,73a,73b M. Delmastro,5 C. Delporte,132 P. A. Delsart,58 D. A. DeMarco,167 S. Demers,183 M. Demichev,79 G. Demontigny,109 S. P. Denisov,123 D. Denysiuk,120 L. D’Eramo,136 D. Derendarz,84 J. E. Derkaoui,35d F. Derue,136 P. Dervan,90 K. Desch,24 C. Deterre,46 K. Dette,167 C. Deutsch,24 M. R. Devesa,30 P. O. Deviveiros,36 A. Dewhurst,144 S. Dhaliwal,26 F. A. Di Bello,54 A. Di Ciaccio,73a,73b L. Di Ciaccio,5 W. K. Di Clemente,137 C. Di Donato,69a,69b A. Di Girolamo,36 G. Di Gregorio,71a,71b B. Di Micco,74a,74b R. Di Nardo,102 K. F. Di Petrillo,59 R. Di Sipio,167 D. Di Valentino,34 C. Diaconu,101 F. A. Dias,40 T. Dias Do Vale,140a M. A. Diaz,147a J. Dickinson,18 E. B. Diehl,105 J. Dietrich,19 S. Díez Cornell,46 A. Dimitrievska,18 W. Ding,15b J. Dingfelder,24 F. Dittus,36 F. Djama,101 T. Djobava,159b J. I. Djuvsland,17 M. A. B. Do Vale,80c M. Dobre,27b D. Dodsworth,26 C. Doglioni,96 J. Dolejsi,143 Z. Dolezal,143 M. Donadelli,80d B. Dong,60c J. Donini,38 A. D’onofrio,92 M. D’Onofrio,90 J. Dopke,144 A. Doria,69a M. T. Dova,88 A. T. Doyle,57 E. Drechsler,152 E. Dreyer,152 T. Dreyer,53 A. S. Drobac,170 Y. Duan,60b F. Dubinin,110 M. Dubovsky,28a A. Dubreuil,54 E. Duchovni,180 G. Duckeck,114 A. Ducourthial,136 O. A. Ducu,109 D. Duda,115 A. Dudarev,36 A. C. Dudder,99 E. M. Duffield,18 L. Duflot,132 M. Dührssen,36 C. Dülsen,182 M. Dumancic,180 A. E. Dumitriu,27b A. K. Duncan,57 M. Dunford,61a A. Duperrin,101 H. Duran Yildiz,4a M. Düren,56 A. Durglishvili,159b D. Duschinger,48 B. Dutta,46 D. Duvnjak,1 G. I. Dyckes,137 M. Dyndal,36 S. Dysch,100 B. S. Dziedzic,84 K. M. Ecker,115 R. C. Edgar,105 T. Eifert,36 052001-9 PHYSICAL REVIEW LETTERS 123, 052001 (2019) G. Eigen,17 K. Einsweiler,18 T. Ekelof,172 H. El Jarrari,35e M. El Kacimi,35c R. El Kosseifi,101 V. Ellajosyula,172 M. Ellert,172 F. Ellinghaus,182 A. A. Elliot,92 N. Ellis,36 J. Elmsheuser,29 M. Elsing,36 D. Emeliyanov,144 A. Emerman,39 Y. Enari,163 M. B. Epland,49 J. Erdmann,47 A. Ereditato,20 M. Errenst,36 M. Escalier,132 C. Escobar,174 O. Estrada Pastor,174 E. Etzion,161 H. Evans,65 A. Ezhilov,138 F. Fabbri,57 L. Fabbri,23b,23a V. Fabiani,119 G. Facini,94 R. M. Faisca Rodrigues Pereira,140a R. M. Fakhrutdinov,123 S. Falciano,72a P. J. Falke,5 S. Falke,5 J. Faltova,143 Y. Fang,15a Y. Fang,15a G. Fanourakis,44 M. Fanti,68a,68b M. Faraj,66a,66c A. Farbin,8 A. Farilla,74a E. M. Farina,70a,70b T. Farooque,106 S. Farrell,18 S. M. Farrington,50 P. Farthouat,36 F. Fassi,35e P. Fassnacht,36 D. Fassouliotis,9 M. Faucci Giannelli,50 W. J. Fawcett,32 L. Fayard,132 O. L. Fedin,138,r W. Fedorko,175 M. Feickert,42 S. Feigl,134 L. Feligioni,101 A. Fell,149 C. Feng,60b E. J. Feng,36 M. Feng,49 M. J. Fenton,57 A. B. Fenyuk,123 J. Ferrando,46 A. Ferrante,173 A. Ferrari,172 P. Ferrari,120 R. Ferrari,70a D. E. Ferreira de Lima,61b A. Ferrer,174 D. Ferrere,54 C. Ferretti,105 F. Fiedler,99 A. Filipčič,91 F. Filthaut,119 K. D. Finelli,25 M. C. N. Fiolhais,140a L. Fiorini,174 F. Fischer,114 W. C. Fisher,106 I. Fleck,151 P. Fleischmann,105 R. R. M. Fletcher,137 T. Flick,182 B. M. Flierl,114 L. F. Flores,137 L. R. Flores Castillo,63a F. M. Follega,75a,75b N. Fomin,17 J. H. Foo,167 G. T. Forcolin,75a,75b A. Formica,145 F. A. Förster,14 A. C. Forti,100 A. G. Foster,21 M. G. Foti,135 D. Fournier,132 H. Fox,89 P. Francavilla,71a,71b S. Francescato,72a,72b M. Franchini,23b,23a S. Franchino,61a D. Francis,36 L. Franconi,20 M. Franklin,59 A. N. Fray,92 B. Freund,109 W. S. Freund,80b E. M. Freundlich,47 D. C. Frizzell,128 D. Froidevaux,36 J. A. Frost,135 C. Fukunaga,164 E. Fullana Torregrosa,174 E. Fumagalli,55b,55a T. Fusayasu,116 J. Fuster,174 A. Gabrielli,23b,23a A. Gabrielli,18 G. P. Gach,83a S. Gadatsch,54 P. Gadow,115 G. Gagliardi,55b,55a L. G. Gagnon,109 C. Galea,27b B. Galhardo,140a G. E. Gallardo,135 E. J. Gallas,135 B. J. Gallop,144 G. Galster,40 R. Gamboa Goni,92 K. K. Gan,126 S. Ganguly,180 J. Gao,60a Y. Gao,50 Y. S. Gao,31,h C. García,174 J. E. García Navarro,174 J. A. García Pascual,15a C. Garcia-Argos,52 M. Garcia-Sciveres,18 R. W. Gardner,37 N. Garelli,153 S. Gargiulo,52 V. Garonne,134 A. Gaudiello,55b,55a G. Gaudio,70a I. L. Gavrilenko,110 A. Gavrilyuk,111 C. Gay,175 G. Gaycken,46 E. N. Gazis,10 A. A. Geanta,27b C. N. P. Gee,144 J. Geisen,53 M. Geisen,99 M. P. Geisler,61a C. Gemme,55b M. H. Genest,58 C. Geng,105 S. Gentile,72a,72b S. George,93 T. Geralis,44 L. O. Gerlach,53 P. Gessinger-Befurt,99 G. Gessner,47 S. Ghasemi,151 M. Ghasemi Bostanabad,176 M. Ghneimat,24 A. Ghosh,132 A. Ghosh,77 B. Giacobbe,23b S. Giagu,72a,72b N. Giangiacomi,23b,23a P. Giannetti,71a A. Giannini,69a,69b S. M. Gibson,93 M. Gignac,146 D. Gillberg,34 G. Gilles,182 D. M. Gingrich,3,e M. P. Giordani,66a,66c F. M. Giorgi,23b P. F. Giraud,145 G. Giugliarelli,66a,66c D. Giugni,68a F. Giuli,73a,73b S. Gkaitatzis,162 I. Gkialas,9,s E. L. Gkougkousis,14 P. Gkountoumis,10 L. K. Gladilin,113 C. Glasman,98 J. Glatzer,14 P. C. F. Glaysher,46 A. Glazov,46 M. Goblirsch-Kolb,26 S. Goldfarb,104 T. Golling,54 D. Golubkov,123 A. Gomes,140a,140b R. Goncalves Gama,53 R. Gonçalo,140a,140b G. Gonella,52 L. Gonella,21 A. Gongadze,79 F. Gonnella,21 J. L. Gonski,59 S. González de la Hoz,174 S. Gonzalez-Sevilla,54 G. R. Gonzalvo Rodriguez,174 L. Goossens,36 P. A. Gorbounov,111 H. A. Gordon,29 B. Gorini,36 E. Gorini,67a,67b A. Gorišek,91 A. T. Goshaw,49 C. Gössling,47 M. I. Gostkin,79 C. A. Gottardo,119 M. Gouighri,35b D. Goujdami,35c A. G. Goussiou,148 N. Govender,33b,t C. Goy,5 E. Gozani,160 I. Grabowska-Bold,83a E. C. Graham,90 J. Gramling,171 E. Gramstad,134 S. Grancagnolo,19 M. Grandi,156 V. Gratchev,138 P. M. Gravila,27f F. G. Gravili,67a,67b C. Gray,57 H. M. Gray,18 C. Grefe,24 K. Gregersen,96 I. M. Gregor,46 P. Grenier,153 K. Grevtsov,46 C. Grieco,14 N. A. Grieser,128 J. Griffiths,8 A. A. Grillo,146 K. Grimm,31,u S. Grinstein,14,v J.-F. Grivaz,132 S. Groh,99 E. Gross,180 J. Grosse-Knetter,53 Z. J. Grout,94 C. Grud,105 A. Grummer,118 L. Guan,105 W. Guan,181 J. Guenther,36 A. Guerguichon,132 J. G. R. Guerrero Rojas,174 F. Guescini,115 D. Guest,171 R. Gugel,52 T. Guillemin,5 S. Guindon,36 U. Gul,57 J. Guo,60c W. Guo,105 Y. Guo,60a,w Z. Guo,101 R. Gupta,46 S. Gurbuz,12c G. Gustavino,128 P. Gutierrez,128 C. Gutschow,94 C. Guyot,145 C. Gwenlan,135 C. B. Gwilliam,90 A. Haas,124 C. Haber,18 H. K. Hadavand,8 N. Haddad,35e A. Hadef,60a S. Hageböck,36 M. Hagihara,169 M. Haleem,177 J. Haley,129 G. Halladjian,106 G. D. Hallewell,101 K. Hamacher,182 P. Hamal,130 K. Hamano,176 H. Hamdaoui,35e G. N. Hamity,149 K. Han,60a,x L. Han,60a S. Han,15a,15d K. Hanagaki,81,y M. Hance,146 D. M. Handl,114 B. Haney,137 R. Hankache,136 P. Hanke,61a E. Hansen,96 J. B. Hansen,40 J. D. Hansen,40 M. C. Hansen,24 P. H. Hansen,40 E. C. Hanson,100 K. Hara,169 A. S. Hard,181 T. Harenberg,182 S. Harkusha,107 P. F. Harrison,178 N. M. Hartmann,114 Y. Hasegawa,150 A. Hasib,50 S. Hassani,145 S. Haug,20 R. Hauser,106 L. B. Havener,39 M. Havranek,142 C. M. Hawkes,21 R. J. Hawkings,36 D. Hayden,106 C. Hayes,155 R. L. Hayes,175 C. P. Hays,135 J. M. Hays,92 H. S. Hayward,90 S. J. Haywood,144 F. He,60a M. P. Heath,50 V. Hedberg,96 L. Heelan,8 S. Heer,24 K. K. Heidegger,52 W. D. Heidorn,78 J. Heilman,34 S. Heim,46 T. Heim,18 B. Heinemann,46,z J. J. Heinrich,131 L. Heinrich,36 C. Heinz,56 J. Hejbal,141 L. Helary,61b A. Held,175 S. Hellesund,134 C. M. Helling,146 S. Hellman,45a,45b C. Helsens,36 R. C. W. Henderson,89 Y. Heng,181 S. Henkelmann,175 A. M. Henriques Correia,36 G. H. Herbert,19 H. Herde,26 V. Herget,177 Y. Hernández Jiménez,33c 052001-10 PHYSICAL REVIEW LETTERS 123, 052001 (2019) H. Herr,99 M. G. Herrmann,114 T. Herrmann,48 G. Herten,52 R. Hertenberger,114 L. Hervas,36 T. C. Herwig,137 G. G. Hesketh,94 N. P. Hessey,168a A. Higashida,163 S. Higashino,81 E. Higón-Rodriguez,174 K. Hildebrand,37 E. Hill,176 J. C. Hill,32 K. K. Hill,29 K. H. Hiller,46 S. J. Hillier,21 M. Hils,48 I. Hinchliffe,18 F. Hinterkeuser,24 M. Hirose,133 S. Hirose,52 D. Hirschbuehl,182 B. Hiti,91 O. Hladik,141 D. R. Hlaluku,33c X. Hoad,50 J. Hobbs,155 N. Hod,180 M. C. Hodgkinson,149 A. Hoecker,36 F. Hoenig,114 D. Hohn,52 D. Hohov,132 T. R. Holmes,37 M. Holzbock,114 L. B. A. H Hommels,32 S. Honda,169 T. Honda,81 T. M. Hong,139 A. Hönle,115 B. H. Hooberman,173 W. H. Hopkins,6 Y. Horii,117 P. Horn,48 L. A. Horyn,37 A. Hostiuc,148 S. Hou,158 A. Hoummada,35a J. Howarth,100 J. Hoya,88 M. Hrabovsky,130 J. Hrdinka,76 I. Hristova,19 J. Hrivnac,132 A. Hrynevich,108 T. Hryn’ova,5 P. J. Hsu,64 S.-C. Hsu,148 Q. Hu,29 S. Hu,60c Y. Huang,15a Z. Hubacek,142 F. Hubaut,101 M. Huebner,24 F. Huegging,24 T. B. Huffman,135 M. Huhtinen,36 R. F. H. Hunter,34 P. Huo,155 A. M. Hupe,34 N. Huseynov,79,aa J. Huston,106 J. Huth,59 R. Hyneman,105 S. Hyrych,28a G. Iacobucci,54 G. Iakovidis,29 I. Ibragimov,151 L. Iconomidou-Fayard,132 Z. Idrissi,35e P. I. Iengo,36 R. Ignazzi,40 O. Igonkina,120,a,bb R. Iguchi,163 T. Iizawa,54 Y. Ikegami,81 M. Ikeno,81 D. Iliadis,162 N. Ilic,119 F. Iltzsche,48 G. Introzzi,70a,70b M. Iodice,74a K. Iordanidou,168a V. Ippolito,72a,72b M. F. Isacson,172 M. Ishino,163 M. Ishitsuka,165 W. Islam,129 C. Issever,135 S. Istin,160 F. Ito,169 J. M. Iturbe Ponce,63a R. Iuppa,75a,75b A. Ivina,180 H. Iwasaki,81 J. M. Izen,43 V. Izzo,69a P. Jacka,141 P. Jackson,1 R. M. Jacobs,24 B. P. Jaeger,152 V. Jain,2 G. Jäkel,182 K. B. Jakobi,99 K. Jakobs,52 S. Jakobsen,76 T. Jakoubek,141 J. Jamieson,57 K. W. Janas,83a R. Jansky,54 J. Janssen,24 M. Janus,53 P. A. Janus,83a G. Jarlskog,96 N. Javadov,79,aa T. Javůrek,36 M. Javurkova,52 F. Jeanneau,145 L. Jeanty,131 J. Jejelava,159a,cc A. Jelinskas,178 P. Jenni,52,dd J. Jeong,46 N. Jeong,46 S. Jézéquel,5 H. Ji,181 J. Jia,155 H. Jiang,78 Y. Jiang,60a Z. Jiang,153,ee S. Jiggins,52 F. A. Jimenez Morales,38 J. Jimenez Pena,115 S. Jin,15c A. Jinaru,27b O. Jinnouchi,165 H. Jivan,33c P. Johansson,149 K. A. Johns,7 C. A. Johnson,65 K. Jon-And,45a,45b R. W. L. Jones,89 S. D. Jones,156 S. Jones,7 T. J. Jones,90 J. Jongmanns,61a P. M. Jorge,140a J. Jovicevic,36 X. Ju,18 J. J. Junggeburth,115 A. Juste Rozas,14,v A. Kaczmarska,84 M. Kado,72a,72b H. Kagan,126 M. Kagan,153 C. Kahra,99 T. Kaji,179 E. Kajomovitz,160 C. W. Kalderon,96 A. Kaluza,99 A. Kamenshchikov,123 L. Kanjir,91 Y. Kano,163 V. A. Kantserov,112 J. Kanzaki,81 L. S. Kaplan,181 D. Kar,33c M. J. Kareem,168b E. Karentzos,10 S. N. Karpov,79 Z. M. Karpova,79 V. Kartvelishvili,89 A. N. Karyukhin,123 L. Kashif,181 R. D. Kass,126 A. Kastanas,45a,45b Y. Kataoka,163 C. Kato,60d,60c J. Katzy,46 K. Kawade,82 K. Kawagoe,87 T. Kawaguchi,117 T. Kawamoto,163 G. Kawamura,53 E. F. Kay,176 V. F. Kazanin,122b,122a R. Keeler,176 R. Kehoe,42 J. S. Keller,34 E. Kellermann,96 D. Kelsey,156 J. J. Kempster,21 J. Kendrick,21 O. Kepka,141 S. Kersten,182 B. P. Kerševan,91 S. Ketabchi Haghighat,167 M. Khader,173 F. Khalil-Zada,13 M. Khandoga,145 A. Khanov,129 A. G. Kharlamov,122b,122a T. Kharlamova,122b,122a E. E. Khoda,175 A. Khodinov,166 T. J. Khoo,54 E. Khramov,79 J. Khubua,159b S. Kido,82 M. Kiehn,54 C. R. Kilby,93 Y. K. Kim,37 N. Kimura,66a,66c O. M. Kind,19 B. T. King,90,a D. Kirchmeier,48 J. Kirk,144 A. E. Kiryunin,115 T. Kishimoto,163 D. P. Kisliuk,167 V. Kitali,46 O. Kivernyk,5 E. Kladiva,28b,a T. Klapdor-Kleingrothaus,52 M. Klassen,61a M. H. Klein,105 M. Klein,90 U. Klein,90 K. Kleinknecht,99 P. Klimek,121 A. Klimentov,29 T. Klingl,24 T. Klioutchnikova,36 F. F. Klitzner,114 P. Kluit,120 S. Kluth,115 E. Kneringer,76 E. B. F. G. Knoops,101 A. Knue,52 D. Kobayashi,87 T. Kobayashi,163 M. Kobel,48 M. Kocian,153 P. Kodys,143 P. T. Koenig,24 T. Koffas,34 N. M. Köhler,36 T. Koi,153 M. Kolb,61b I. Koletsou,5 T. Komarek,130 T. Kondo,81 N. Kondrashova,60c K. Köneke,52 A. C. König,119 T. Kono,125 R. Konoplich,124,ff V. Konstantinides,94 N. Konstantinidis,94 B. Konya,96 R. Kopeliansky,65 S. Koperny,83a K. Korcyl,84 K. Kordas,162 G. Koren,161 A. Korn,94 I. Korolkov,14 E. V. Korolkova,149 N. Korotkova,113 O. Kortner,115 S. Kortner,115 T. Kosek,143 V. V. Kostyukhin,24 A. Kotwal,49 A. Koulouris,10 A. Kourkoumeli-Charalampidi,70a,70b C. Kourkoumelis,9 E. Kourlitis,149 V. Kouskoura,29 A. B. Kowalewska,84 R. Kowalewski,176 C. Kozakai,163 W. Kozanecki,145 A. S. Kozhin,123 V. A. Kramarenko,113 G. Kramberger,91 D. Krasnopevtsev,60a M. W. Krasny,136 A. Krasznahorkay,36 D. Krauss,115 J. A. Kremer,83a J. Kretzschmar,90 P. Krieger,167 F. Krieter,114 A. Krishnan,61b K. Krizka,18 K. Kroeninger,47 H. Kroha,115 J. Kroll,141 J. Kroll,137 J. Krstic,16 U. Kruchonak,79 H. Krüger,24 N. Krumnack,78 M. C. Kruse,49 J. A. Krzysiak,84 T. Kubota,104 O. Kuchinskaia,166 S. Kuday,4b J. T. Kuechler,46 S. Kuehn,36 A. Kugel,61a T. Kuhl,46 V. Kukhtin,79 R. Kukla,101 Y. Kulchitsky,107,gg S. Kuleshov,147b Y. P. Kulinich,173 M. Kuna,58 T. Kunigo,85 A. Kupco,141 T. Kupfer,47 O. Kuprash,52 H. Kurashige,82 L. L. Kurchaninov,168a Y. A. Kurochkin,107 A. Kurova,112 M. G. Kurth,15a,15d E. S. Kuwertz,36 M. Kuze,165 A. K. Kvam,148 J. Kvita,130 T. Kwan,103 A. La Rosa,115 L. La Rotonda,41b,41a F. La Ruffa,41b,41a C. Lacasta,174 F. Lacava,72a,72b D. P. J. Lack,100 H. Lacker,19 D. Lacour,136 E. Ladygin,79 R. Lafaye,5 B. Laforge,136 T. Lagouri,33c S. Lai,53 S. Lammers,65 W. Lampl,7 C. Lampoudis,162 E. Lançon,29 U. Landgraf,52 M. P. J. Landon,92 M. C. Lanfermann,54 V. S. Lang,46 J. C. Lange,53 R. J. Langenberg,36 A. J. Lankford,171 F. Lanni,29 K. Lantzsch,24 A. Lanza,70a A. Lapertosa,55b,55a S. Laplace,136 J. F. Laporte,145 T. Lari,68a F. Lasagni Manghi,23b,23a M. Lassnig,36 T. S. Lau,63a A. Laudrain,132 A. Laurier,34 052001-11 PHYSICAL REVIEW LETTERS 123, 052001 (2019) M. Lavorgna,69a,69b M. Lazzaroni,68a,68b B. Le,104 O. Le Dortz,136 E. Le Guirriec,101 M. LeBlanc,7 T. LeCompte,6 F. Ledroit-Guillon,58 C. A. Lee,29 G. R. Lee,17 L. Lee,59 S. C. Lee,158 S. J. Lee,34 B. Lefebvre,168a M. Lefebvre,176 F. Legger,114 C. Leggett,18 K. Lehmann,152 N. Lehmann,182 G. Lehmann Miotto,36 W. A. Leight,46 A. Leisos,162,hh M. A. L. Leite,80d C. E. Leitgeb,114 R. Leitner,143 D. Lellouch,180,a K. J. C. Leney,42 T. Lenz,24 B. Lenzi,36 R. Leone,7 S. Leone,71a C. Leonidopoulos,50 A. Leopold,136 G. Lerner,156 C. Leroy,109 R. Les,167 C. G. Lester,32 M. Levchenko,138 J. Levêque,5 D. Levin,105 L. J. Levinson,180 D. J. Lewis,21 B. Li,15b B. Li,105 C-Q. Li,60a F. Li,60c H. Li,60a H. Li,60b J. Li,60c K. Li,153 L. Li,60c M. Li,15a Q. Li,15a,15d Q. Y. Li,60a S. Li,60d,60c X. Li,46 Y. Li,46 Z. Li,60b Z. Liang,15a B. Liberti,73a A. Liblong,167 K. Lie,63c S. Liem,120 C. Y. Lin,32 K. Lin,106 T. H. Lin,99 R. A. Linck,65 J. H. Lindon,21 A. L. Lionti,54 E. Lipeles,137 A. Lipniacka,17 M. Lisovyi,61b T. M. Liss,173,ii A. Lister,175 A. M. Litke,146 J. D. Little,8 B. Liu,78,jj B. L Liu,6 H. B. Liu,29 H. Liu,105 J. B. Liu,60a J. K. K. Liu,135 K. Liu,136 M. Liu,60a P. Liu,18 Y. Liu,15a,15d Y. L. Liu,105 Y. W. Liu,60a M. Livan,70a,70b A. Lleres,58 J. Llorente Merino,15a S. L. Lloyd,92 C. Y. Lo,63b F. Lo Sterzo,42 E. M. Lobodzinska,46 P. Loch,7 S. Loffredo,73a,73b T. Lohse,19 K. Lohwasser,149 M. Lokajicek,141 J. D. Long,173 R. E. Long,89 L. Longo,36 K. A. Looper,126 J. A. Lopez,147b I. Lopez Paz,100 A. Lopez Solis,149 J. Lorenz,114 N. Lorenzo Martinez,5 M. Losada,22 P. J. Lösel,114 A. Lösle,52 X. Lou,46 X. Lou,15a A. Lounis,132 J. Love,6 P. A. Love,89 J. J. Lozano Bahilo,174 M. Lu,60a Y. J. Lu,64 H. J. Lubatti,148 C. Luci,72a,72b A. Lucotte,58 C. Luedtke,52 F. Luehring,65 I. Luise,136 L. Luminari,72a B. Lund-Jensen,154 M. S. Lutz,102 D. Lynn,29 R. Lysak,141 E. Lytken,96 F. Lyu,15a V. Lyubushkin,79 T. Lyubushkina,79 H. Ma,29 L. L. Ma,60b Y. Ma,60b G. Maccarrone,51 A. Macchiolo,115 C. M. Macdonald,149 J. Machado Miguens,137 D. Madaffari,174 R. Madar,38 W. F. Mader,48 N. Madysa,48 J. Maeda,82 K. Maekawa,163 S. Maeland,17 T. Maeno,29 M. Maerker,48 A. S. Maevskiy,113 V. Magerl,52 N. Magini,78 D. J. Mahon,39 C. Maidantchik,80b T. Maier,114 A. Maio,140a,140b,140d O. Majersky,28a S. Majewski,131 Y. Makida,81 N. Makovec,132 B. Malaescu,136 Pa. Malecki,84 V. P. Maleev,138 F. Malek,58 U. Mallik,77 D. Malon,6 C. Malone,32 S. Maltezos,10 S. Malyukov,36 J. Mamuzic,174 G. Mancini,51 I. Mandić,91 L. Manhaes de Andrade Filho,80a I. M. Maniatis,162 J. Manjarres Ramos,48 K. H. Mankinen,96 A. Mann,114 A. Manousos,76 B. Mansoulie,145 I. Manthos,162 S. Manzoni,120 A. Marantis,162 G. Marceca,30 L. Marchese,135 G. Marchiori,136 M. Marcisovsky,141 C. Marcon,96 C. A. Marin Tobon,36 M. Marjanovic,38 F. Marroquim,80b Z. Marshall,18 M. U. F Martensson,172 S. Marti-Garcia,174 C. B. Martin,126 T. A. Martin,178 V. J. Martin,50 B. Martin dit Latour,17 L. Martinelli,74a,74b M. Martinez,14,v V. I. Martinez Outschoorn,102 S. Martin-Haugh,144 V. S. Martoiu,27b A. C. Martyniuk,94 A. Marzin,36 S. R. Maschek,115 L. Masetti,99 T. Mashimo,163 R. Mashinistov,110 J. Masik,100 A. L. Maslennikov,122b,122a L. H. Mason,104 L. Massa,73a,73b P. Massarotti,69a,69b P. Mastrandrea,71a,71b A. Mastroberardino,41b,41a T. Masubuchi,163 D. Matakias,10 A. Matic,114 P. Mättig,24 J. Maurer,27b B. Maček,91 S. J. Maxfield,90 D. A. Maximov,122b,122a R. Mazini,158 I. Maznas,162 S. M. Mazza,146 S. P. Mc Kee,105 T. G. McCarthy,115 L. I. McClymont,94 W. P. McCormack,18 E. F. McDonald,104 J. A. Mcfayden,36 M. A. McKay,42 K. D. McLean,176 S. J. McMahon,144 P. C. McNamara,104 C. J. McNicol,178 R. A. McPherson,176,p J. E. Mdhluli,33c Z. A. Meadows,102 S. Meehan,148 T. Megy,52 S. Mehlhase,114 A. Mehta,90 T. Meideck,58 B. Meirose,43 D. Melini,174 B. R. Mellado Garcia,33c J. D. Mellenthin,53 M. Melo,28a F. Meloni,46 A. Melzer,24 S. B. Menary,100 E. D. Mendes Gouveia,140a,140e L. Meng,36 X. T. Meng,105 S. Menke,115 E. Meoni,41b,41a S. Mergelmeyer,19 S. A. M. Merkt,139 C. Merlassino,20 P. Mermod,54 L. Merola,69a,69b C. Meroni,68a O. Meshkov,113,110 J. K. R. Meshreki,151 A. Messina,72a,72b J. Metcalfe,6 A. S. Mete,171 C. Meyer,65 J. Meyer,160 J-P. Meyer,145 H. Meyer Zu Theenhausen,61a F. Miano,156 M. Michetti,19 R. P. Middleton,144 L. Mijović,50 G. Mikenberg,180 M. Mikestikova,141 M. Mikuž,91 H. Mildner,149 M. Milesi,104 A. Milic,167 D. A. Millar,92 D. W. Miller,37 A. Milov,180 D. A. Milstead,45a,45b R. A. Mina,153,ee A. A. Minaenko,123 M. Miñano Moya,174 I. A. Minashvili,159b A. I. Mincer,124 B. Mindur,83a M. Mineev,79 Y. Minegishi,163 Y. Ming,181 L. M. Mir,14 A. Mirto,67a,67b K. P. Mistry,137 T. Mitani,179 J. Mitrevski,114 V. A. Mitsou,174 M. Mittal,60c A. Miucci,20 P. S. Miyagawa,149 A. Mizukami,81 J. U. Mjörnmark,96 T. Mkrtchyan,184 M. Mlynarikova,143 T. Moa,45a,45b K. Mochizuki,109 P. Mogg,52 S. Mohapatra,39 R. Moles-Valls,24 M. C. Mondragon,106 K. Mönig,46 J. Monk,40 E. Monnier,101 A. Montalbano,152 J. Montejo Berlingen,36 M. Montella,94 F. Monticelli,88 S. Monzani,68a N. Morange,132 D. Moreno,22 M. Moreno Llácer,36 C. Moreno Martinez,14 P. Morettini,55b M. Morgenstern,120 S. Morgenstern,48 D. Mori,152 M. Morii,59 M. Morinaga,179 V. Morisbak,134 A. K. Morley,36 G. Mornacchi,36 A. P. Morris,94 L. Morvaj,155 P. Moschovakos,36 B. Moser,120 M. Mosidze,159b T. Moskalets,145 H. J. Moss,149 J. Moss,31,kk K. Motohashi,165 E. Mountricha,36 E. J. W. Moyse,102 S. Muanza,101 J. Mueller,139 R. S. P. Mueller,114 D. Muenstermann,89 G. A. Mullier,96 J. L. Munoz Martinez,14 F. J. Munoz Sanchez,100 P. Murin,28b W. J. Murray,178,144 A. Murrone,68a,68b M. Muškinja,18 C. Mwewa,33a A. G. Myagkov,123,ll J. Myers,131 M. Myska,142 052001-12 PHYSICAL REVIEW LETTERS 123, 052001 (2019) B. P. Nachman,18 O. Nackenhorst,47 A. Nag Nag,48 K. Nagai,135 K. Nagano,81 Y. Nagasaka,62 M. Nagel,52 E. Nagy,101 A. M. Nairz,36 Y. Nakahama,117 K. Nakamura,81 T. Nakamura,163 I. Nakano,127 H. Nanjo,133 F. Napolitano,61a R. F. Naranjo Garcia,46 R. Narayan,42 I. Naryshkin,138 T. Naumann,46 G. Navarro,22 H. A. Neal,105,a P. Y. Nechaeva,110 F. Nechansky,46 T. J. Neep,21 A. Negri,70a,70b M. Negrini,23b C. Nellist,53 M. E. Nelson,135 S. Nemecek,141 P. Nemethy,124 M. Nessi,36,mm M. S. Neubauer,173 F. Neuhaus,99 M. Neumann,182 P. R. Newman,21 Y. S. Ng,19 Y. W. Y. Ng,171 H. D. N. Nguyen,101 T. Nguyen Manh,109 E. Nibigira,38 R. B. Nickerson,135 R. Nicolaidou,145 D. S. Nielsen,40 J. Nielsen,146 N. Nikiforou,11 V. Nikolaenko,123,ll I. Nikolic-Audit,136 K. Nikolopoulos,21 P. Nilsson,29 H. R. Nindhito,54 Y. Ninomiya,81 A. Nisati,72a N. Nishu,60c R. Nisius,115 I. Nitsche,47 T. Nitta,179 T. Nobe,163 Y. Noguchi,85 I. Nomidis,136 M. A. Nomura,29 M. Nordberg,36 N. Norjoharuddeen,135 T. Novak,91 O. Novgorodova,48 R. Novotny,142 L. Nozka,130 K. Ntekas,171 E. Nurse,94 F. G. Oakham,34,e H. Oberlack,115 J. Ocariz,136 A. Ochi,82 I. Ochoa,39 J. P. Ochoa-Ricoux,147a K. O’Connor,26 S. Oda,87 S. Odaka,81 S. Oerdek,53 A. Ogrodnik,83a A. Oh,100 S. H. Oh,49 C. C. Ohm,154 H. Oide,55b,55a M. L. Ojeda,167 H. Okawa,169 Y. Okazaki,85 Y. Okumura,163 T. Okuyama,81 A. Olariu,27b L. F. Oleiro Seabra,140a S. A. Olivares Pino,147a D. Oliveira Damazio,29 J. L. Oliver,1 M. J. R. Olsson,171 A. Olszewski,84 J. Olszowska,84 D. C. O’Neil,152 A. Onofre,140a,140e K. Onogi,117 P. U. E. Onyisi,11 H. Oppen,134 M. J. Oreglia,37 G. E. Orellana,88 Y. Oren,161 D. Orestano,74a,74b N. Orlando,14 R. S. Orr,167 V. O’Shea,57 R. Ospanov,60a G. Otero y Garzon,30 H. Otono,87 P. S. Ott,61a M. Ouchrif,35d J. Ouellette,29 F. Ould-Saada,134 A. Ouraou,145 Q. Ouyang,15a M. Owen,57 R. E. Owen,21 V. E. Ozcan,12c N. Ozturk,8 J. Pacalt,130 H. A. Pacey,32 K. Pachal,49 A. Pacheco Pages,14 C. Padilla Aranda,14 S. Pagan Griso,18 M. Paganini,183 G. Palacino,65 S. Palazzo,50 S. Palestini,36 M. Palka,83b D. Pallin,38 P. Palni,83a I. Panagoulias,10 C. E. Pandini,36 J. G. Panduro Vazquez,93 P. Pani,46 G. Panizzo,66a,66c L. Paolozzi,54 C. Papadatos,109 K. Papageorgiou,9,s A. Paramonov,6 D. Paredes Hernandez,63b S. R. Paredes Saenz,135 B. Parida,166 T. H. Park,167 A. J. Parker,89 M. A. Parker,32 F. Parodi,55b,55a E. W. P. Parrish,121 J. A. Parsons,39 U. Parzefall,52 L. Pascual Dominguez,136 V. R. Pascuzzi,167 J. M. P. Pasner,146 E. Pasqualucci,72a S. Passaggio,55b F. Pastore,93 P. Pasuwan,45a,45b S. Pataraia,99 J. R. Pater,100 A. Pathak,181 T. Pauly,36 B. Pearson,115 M. Pedersen,134 L. Pedraza Diaz,119 R. Pedro,140a T. Peiffer,53 S. V. Peleganchuk,122b,122a O. Penc,141 H. Peng,60a B. S. Peralva,80a M. M. Perego,132 A. P. Pereira Peixoto,140a D. V. Perepelitsa,29 F. Peri,19 L. Perini,68a,68b H. Pernegger,36 S. Perrella,69a,69b K. Peters,46 R. F. Y. Peters,100 B. A. Petersen,36 T. C. Petersen,40 E. Petit,101 A. Petridis,1 C. Petridou,162 P. Petroff,132 M. Petrov,135 F. Petrucci,74a,74b M. Pettee,183 N. E. Pettersson,102 K. Petukhova,143 A. Peyaud,145 R. Pezoa,147b L. Pezzotti,70a,70b T. Pham,104 F. H. Phillips,106 P. W. Phillips,144 M. W. Phipps,173 G. Piacquadio,155 E. Pianori,18 A. Picazio,102 R. H. Pickles,100 R. Piegaia,30 D. Pietreanu,27b J. E. Pilcher,37 A. D. Pilkington,100 M. Pinamonti,73a,73b J. L. Pinfold,3 M. Pitt,180 L. Pizzimento,73a,73b M.-A. Pleier,29 V. Pleskot,143 E. Plotnikova,79 P. Podberezko,122b,122a R. Poettgen,96 R. Poggi,54 L. Poggioli,132 I. Pogrebnyak,106 D. Pohl,24 I. Pokharel,53 G. Polesello,70a A. Poley,18 A. Policicchio,72a,72b R. Polifka,143 A. Polini,23b C. S. Pollard,46 V. Polychronakos,29 D. Ponomarenko,112 L. Pontecorvo,36 S. Popa,27a G. A. Popeneciu,27d D. M. Portillo Quintero,58 S. Pospisil,142 K. Potamianos,46 I. N. Potrap,79 C. J. Potter,32 H. Potti,11 T. Poulsen,96 J. Poveda,36 T. D. Powell,149 G. Pownall,46 M. E. Pozo Astigarraga,36 P. Pralavorio,101 S. Prell,78 D. Price,100 M. Primavera,67a S. Prince,103 M. L. Proffitt,148 N. Proklova,112 K. Prokofiev,63c F. Prokoshin,79 S. Protopopescu,29 J. Proudfoot,6 M. Przybycien,83a D. Pudzha,138 A. Puri,173 P. Puzo,132 J. Qian,105 Y. Qin,100 A. Quadt,53 M. Queitsch-Maitland,46 A. Qureshi,1 P. Rados,104 F. Ragusa,68a,68b G. Rahal,97 J. A. Raine,54 S. Rajagopalan,29 A. Ramirez Morales,92 K. Ran,15a,15d T. Rashid,132 S. Raspopov,5 D. M. Rauch,46 F. Rauscher,114 S. Rave,99 B. Ravina,149 I. Ravinovich,180 J. H. Rawling,100 M. Raymond,36 A. L. Read,134 N. P. Readioff,58 M. Reale,67a,67b D. M. Rebuzzi,70a,70b A. Redelbach,177 G. Redlinger,29 K. Reeves,43 L. Rehnisch,19 J. Reichert,137 D. Reikher,161 A. Reiss,99 A. Rej,151 C. Rembser,36 M. Renda,27b M. Rescigno,72a S. Resconi,68a E. D. Resseguie,137 S. Rettie,175 E. Reynolds,21 O. L. Rezanova,122b,122a P. Reznicek,143 E. Ricci,75a,75b R. Richter,115 S. Richter,46 E. Richter-Was,83b O. Ricken,24 M. Ridel,136 P. Rieck,115 C. J. Riegel,182 O. Rifki,46 M. Rijssenbeek,155 A. Rimoldi,70a,70b M. Rimoldi,46 L. Rinaldi,23b G. Ripellino,154 B. Ristić,89 I. Riu,14 J. C. Rivera Vergara,176 F. Rizatdinova,129 E. Rizvi,92 C. Rizzi,36 R. T. Roberts,100 S. H. Robertson,103,p M. Robin,46 D. Robinson,32 J. E. M. Robinson,46 C. M. Robles Gajardo,147b A. Robson,57 E. Rocco,99 C. Roda,71a,71b S. Rodriguez Bosca,174 A. Rodriguez Perez,14 D. Rodriguez Rodriguez,174 A. M. Rodríguez Vera,168b S. Roe,36 O. Røhne,134 R. Röhrig,115 C. P. A. Roland,65 J. Roloff,59 A. Romaniouk,112 M. Romano,23b,23a N. Rompotis,90 M. Ronzani,124 L. Roos,136 S. Rosati,72a K. Rosbach,52 G. Rosin,102 B. J. Rosser,137 E. Rossi,46 E. Rossi,74a,74b E. Rossi,69a,69b L. P. Rossi,55b L. Rossini,68a,68b R. Rosten,14 M. Rotaru,27b J. Rothberg,148 D. Rousseau,132 G. Rovelli,70a,70b A. Roy,11 D. Roy,33c A. Rozanov,101 Y. Rozen,160 X. Ruan,33c F. Rubbo,153 F. Rühr,52 A. Ruiz-Martinez,174 A. Rummler,36 052001-13 PHYSICAL REVIEW LETTERS 123, 052001 (2019) Z. Rurikova,52 N. A. Rusakovich,79 H. L. Russell,103 L. Rustige,38,47 J. P. Rutherfoord,7 E. M. Rüttinger,46,nn Y. F. Ryabov,138 M. Rybar,39 G. Rybkin,132 E. B. Rye,134 A. Ryzhov,123 G. F. Rzehorz,53 P. Sabatini,53 G. Sabato,120 S. Sacerdoti,132 H. F-W. Sadrozinski,146 R. Sadykov,79 F. Safai Tehrani,72a B. Safarzadeh Samani,156 P. Saha,121 S. Saha,103 M. Sahinsoy,61a A. Sahu,182 M. Saimpert,46 M. Saito,163 T. Saito,163 H. Sakamoto,163 A. Sakharov,124,ff D. Salamani,54 G. Salamanna,74a,74b J. E. Salazar Loyola,147b P. H. Sales De Bruin,172 A. Salnikov,153 J. Salt,174 D. Salvatore,41b,41a F. Salvatore,156 A. Salvucci,63a,63b,63c A. Salzburger,36 J. Samarati,36 D. Sammel,52 D. Sampsonidis,162 D. Sampsonidou,162 J. Sánchez,174 A. Sanchez Pineda,66a,66c H. Sandaker,134 C. O. Sander,46 I. G. Sanderswood,89 M. Sandhoff,182 C. Sandoval,22 D. P. C. Sankey,144 M. Sannino,55b,55a Y. Sano,117 A. Sansoni,51 C. Santoni,38 H. Santos,140a,140b S. N. Santpur,18 A. Santra,174 A. Sapronov,79 J. G. Saraiva,140a,140d O. Sasaki,81 K. Sato,169 E. Sauvan,5 P. Savard,167,e N. Savic,115 R. Sawada,163 C. Sawyer,144 L. Sawyer,95,oo C. Sbarra,23b A. Sbrizzi,23a T. Scanlon,94 J. Schaarschmidt,148 P. Schacht,115 B. M. Schachtner,114 D. Schaefer,37 L. Schaefer,137 J. Schaeffer,99 S. Schaepe,36 U. Schäfer,99 A. C. Schaffer,132 D. Schaile,114 R. D. Schamberger,155 N. Scharmberg,100 V. A. Schegelsky,138 D. Scheirich,143 F. Schenck,19 M. Schernau,171 C. Schiavi,55b,55a S. Schier,146 L. K. Schildgen,24 Z. M. Schillaci,26 E. J. Schioppa,36 M. Schioppa,41b,41a K. E. Schleicher,52 S. Schlenker,36 K. R. Schmidt-Sommerfeld,115 K. Schmieden,36 C. Schmitt,99 S. Schmitt,46 S. Schmitz,99 J. C. Schmoeckel,46 U. Schnoor,52 L. Schoeffel,145 A. Schoening,61b P. G. Scholer,52 E. Schopf,135 M. Schott,99 J. F. P. Schouwenberg,119 J. Schovancova,36 S. Schramm,54 F. Schroeder,182 A. Schulte,99 H-C. Schultz-Coulon,61a M. Schumacher,52 B. A. Schumm,146 Ph. Schune,145 A. Schwartzman,153 T. A. Schwarz,105 Ph. Schwemling,145 R. Schwienhorst,106 A. Sciandra,146 G. Sciolla,26 M. Scodeggio,46 M. Scornajenghi,41b,41a F. Scuri,71a F. Scutti,104 L. M. Scyboz,115 C. D. Sebastiani,72a,72b P. Seema,19 S. C. Seidel,118 A. Seiden,146 T. Seiss,37 J. M. Seixas,80b G. Sekhniaidze,69a K. Sekhon,105 S. J. Sekula,42 N. Semprini-Cesari,23b,23a S. Sen,49 S. Senkin,38 C. Serfon,76 L. Serin,132 L. Serkin,66a,66b M. Sessa,60a H. Severini,128 F. Sforza,170 A. Sfyrla,54 E. Shabalina,53 J. D. Shahinian,146 N. W. Shaikh,45a,45b D. Shaked Renous,180 L. Y. Shan,15a R. Shang,173 J. T. Shank,25 M. Shapiro,18 A. Sharma,135 A. S. Sharma,1 P. B. Shatalov,111 K. Shaw,156 S. M. Shaw,100 A. Shcherbakova,138 Y. Shen,128 N. Sherafati,34 A. D. Sherman,25 P. Sherwood,94 L. Shi,158,pp S. Shimizu,81 C. O. Shimmin,183 Y. Shimogama,179 M. Shimojima,116 I. P. J. Shipsey,135 S. Shirabe,87 M. Shiyakova,79,qq J. Shlomi,180 A. Shmeleva,110 M. J. Shochet,37 S. Shojaii,104 D. R. Shope,128 S. Shrestha,126 E. M. Shrif,33c E. Shulga,180 P. Sicho,141 A. M. Sickles,173 P. E. Sidebo,154 E. Sideras Haddad,33c O. Sidiropoulou,36 A. Sidoti,23b,23a F. Siegert,48 Dj. Sijacki,16 M. Silva Jr.,181 M. V. Silva Oliveira,80a S. B. Silverstein,45a S. Simion,132 E. Simioni,99 R. Simoniello,99 S. Simsek,12b P. Sinervo,167 V. Sinetckii,113,110 N. B. Sinev,131 M. Sioli,23b,23a I. Siral,105 S. Yu. Sivoklokov,113 J. Sjölin,45a,45b E. Skorda,96 P. Skubic,128 M. Slawinska,84 K. Sliwa,170 R. Slovak,143 V. Smakhtin,180 B. H. Smart,144 J. Smiesko,28a N. Smirnov,112 S. Yu. Smirnov,112 Y. Smirnov,112 L. N. Smirnova,113,rr O. Smirnova,96 J. W. Smith,53 M. Smizanska,89 K. Smolek,142 A. Smykiewicz,84 A. A. Snesarev,110 H. L. Snoek,120 I. M. Snyder,131 S. Snyder,29 R. Sobie,176,p A. M. Soffa,171 A. Soffer,161 A. Søgaard,50 F. Sohns,53 C. A. Solans Sanchez,36 E. Yu. Soldatov,112 U. Soldevila,174 A. A. Solodkov,123 A. Soloshenko,79 O. V. Solovyanov,123 V. Solovyev,138 P. Sommer,149 H. Son,170 W. Song,144 W. Y. Song,168b A. Sopczak,142 F. Sopkova,28b C. L. Sotiropoulou,71a,71b S. Sottocornola,70a,70b R. Soualah,66a,66c,ss A. M. Soukharev,122b,122a D. South,46 S. Spagnolo,67a,67b M. Spalla,115 M. Spangenberg,178 F. Spanò,93 D. Sperlich,52 T. M. Spieker,61a R. Spighi,23b G. Spigo,36 M. Spina,156 D. P. Spiteri,57 M. Spousta,143 A. Stabile,68a,68b B. L. Stamas,121 R. Stamen,61a M. Stamenkovic,120 E. Stanecka,84 R. W. Stanek,6 B. Stanislaus,135 M. M. Stanitzki,46 M. Stankaityte,135 B. Stapf,120 E. A. 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Zeitnitz,182 G. Zemaityte,135 J. C. Zeng,173 O. Zenin,123 D. Zerwas,132 M. Zgubič,135 D. F. Zhang,15b F. Zhang,181 G. Zhang,60a G. Zhang,15b H. Zhang,15c J. Zhang,6 L. Zhang,15c L. Zhang,60a M. Zhang,173 R. Zhang,60a R. Zhang,24 X. Zhang,60b Y. Zhang,15a,15d Z. Zhang,63a Z. Zhang,132 P. Zhao,49 Y. Zhao,60b 052001-15 PHYSICAL REVIEW LETTERS 123, 052001 (2019) Z. Zhao,60a A. Zhemchugov,79 Z. Zheng,105 D. Zhong,173 B. Zhou,105 C. Zhou,181 M. S. Zhou,15a,15d M. Zhou,155 N. Zhou,60c Y. Zhou,7 C. G. Zhu,60b H. L. Zhu,60a H. Zhu,15a J. Zhu,105 Y. Zhu,60a X. Zhuang,15a K. Zhukov,110 V. Zhulanov,122b,122a D. Zieminska,65 N. I. Zimine,79 S. Zimmermann,52 Z. Zinonos,115 M. Ziolkowski,151 G. Zobernig,181 A. Zoccoli,23b,23a K. Zoch,53 T. G. Zorbas,149 R. Zou,37 and L. Zwalinski36 (ATLAS Collaboration) 1 Department of Physics, University of Adelaide, Adelaide, Australia 2 Physics Department, SUNY Albany, Albany, New York, USA 3 Department of Physics, University of Alberta, Edmonton Alberta, Canada 4a Department of Physics, Ankara University, Ankara, Turkey 4b Istanbul Aydin University, Istanbul, Turkey 4c Division of Physics, TOBB University of Economics and Technology, Ankara, Turkey 5 LAPP, Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, Annecy, France 6 High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois, USA 7 Department of Physics, University of Arizona, Tucson, Arizona, USA 8 Department of Physics, University of Texas at Arlington, Arlington, Texas, USA 9 Physics Department, National and Kapodistrian University of Athens, Athens, Greece 10 Physics Department, National Technical University of Athens, Zografou, Greece 11 Department of Physics, University of Texas at Austin, Austin, Texas, USA 12a Bahcesehir University, Faculty of Engineering and Natural Sciences, Istanbul, Turkey 12b Istanbul Bilgi University, Faculty of Engineering and Natural Sciences, Istanbul, Turkey 12c Department of Physics, Bogazici University, Istanbul, Turkey 12d Department of Physics Engineering, Gaziantep University, Gaziantep, Turkey 13 Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan 14 Institut de Física d’Altes Energies (IFAE), Barcelona Institute of Science and Technology, Barcelona, Spain 15a Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China 15b Physics Department, Tsinghua University, Beijing, China 15c Department of Physics, Nanjing University, Nanjing, China 15d University of Chinese Academy of Science (UCAS), Beijing, China 16 Institute of Physics, University of Belgrade, Belgrade, Serbia 17 Department for Physics and Technology, University of Bergen, Bergen, Norway 18 Physics Division, Lawrence Berkeley National Laboratory and University of California, Berkeley, California, USA 19 Institut für Physik, Humboldt Universität zu Berlin, Berlin, Germany 20 Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics, University of Bern, Bern, Switzerland 21 School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom 22 Facultad de Ciencias y Centro de Investigaciónes, Universidad Antonio Nariño, Bogota, Colombia 23a INFN Bologna and Universita’ di Bologna, Dipartimento di Fisica, Italy 23b INFN Sezione di Bologna, Italy 24 Physikalisches Institut, Universität Bonn, Bonn, Germany 25 Department of Physics, Boston University, Boston, Massachusetts, USA 26 Department of Physics, Brandeis University, Waltham, Massachusetts, USA 27a Transilvania University of Brasov, Brasov, Romania 27b Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania 27c Department of Physics, Alexandru Ioan Cuza University of Iasi, Iasi, Romania 27d National Institute for Research and Development of Isotopic and Molecular Technologies, Physics Department, Cluj-Napoca, Romania 27e University Politehnica Bucharest, Bucharest, Romania 27f West University in Timisoara, Timisoara, Romania 28a Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovak Republic 28b Department of Subnuclear Physics, Institute of Experimental Physics of the Slovak Academy of Sciences, Kosice, Slovak Republic 29 Physics Department, Brookhaven National Laboratory, Upton, New York, USA 30 Departamento de Física, Universidad de Buenos Aires, Buenos Aires, Argentina 31 California State University, California, USA 32 Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 33a Department of Physics, University of Cape Town, Cape Town, South Africa 33b Department of Mechanical Engineering Science, University of Johannesburg, Johannesburg, South Africa 33c School of Physics, University of the Witwatersrand, Johannesburg, South Africa 052001-16 PHYSICAL REVIEW LETTERS 123, 052001 (2019) 34 Department of Physics, Carleton University, Ottawa, Ontario, Canada 35a Faculté des Sciences Ain Chock, Réseau Universitaire de Physique des Hautes Energies—Université Hassan II, Casablanca, Morocco 35b Faculté des Sciences, Université Ibn-Tofail, Kénitra, Morocco 35c Faculté des Sciences Semlalia, Université Cadi Ayyad, LPHEA-Marrakech, Morocco 35d Faculté des Sciences, Université Mohamed Premier and LPTPM, Oujda, Morocco 35e Faculté des sciences, Université Mohammed V, Rabat, Morocco 36 CERN, Geneva, Switzerland 37 Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA 38 LPC, Université Clermont Auvergne, CNRS/IN2P3, Clermont-Ferrand, France 39 Nevis Laboratory, Columbia University, Irvington, New York, USA 40 Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark 41a Dipartimento di Fisica, Università della Calabria, Rende, Italy 41b INFN Gruppo Collegato di Cosenza, Laboratori Nazionali di Frascati, Italy 42 Physics Department, Southern Methodist University, Dallas, Texas, USA 43 Physics Department, University of Texas at Dallas, Richardson, Texas, USA 44 National Centre for Scientific Research “Demokritos”, Agia Paraskevi, Greece 45a Department of Physics, Stockholm University, Sweden 45b Oskar Klein Centre, Stockholm, Sweden 46 Deutsches Elektronen-Synchrotron DESY, Hamburg and Zeuthen, Germany 47 Lehrstuhl für Experimentelle Physik IV, Technische Universität Dortmund, Dortmund, Germany 48 Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany 49 Department of Physics, Duke University, Durham, North Carolina, USA 50 SUPA—School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 51 INFN e Laboratori Nazionali di Frascati, Frascati, Italy 52 Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany 53 II. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany 54 Département de Physique Nucléaire et Corpusculaire, Université de Genève, Genève, Switzerland 55a Dipartimento di Fisica, Università di Genova, Genova, Italy 55b INFN Sezione di Genova, Italy 56 II. Physikalisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany 57 SUPA—School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom 58 LPSC, Université Grenoble Alpes, CNRS/IN2P3, Grenoble INP, Grenoble, France 59 Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, Massachusetts, USA 60a Department of Modern Physics and State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei, China 60b Institute of Frontier and Interdisciplinary Science and Key Laboratory of Particle Physics and Particle Irradiation (MOE), Shandong University, Qingdao, China 60c School of Physics and Astronomy, Shanghai Jiao Tong University, KLPPAC-MoE, SKLPPC, Shanghai, China 60d Tsung-Dao Lee Institute, Shanghai, China 61a Kirchhoff-Institut für Physik, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany 61b Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany 62 Faculty of Applied Information Science, Hiroshima Institute of Technology, Hiroshima, Japan 63a Department of Physics, Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China 63b Department of Physics, University of Hong Kong, Hong Kong, China 63c Department of Physics and Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China 64 Department of Physics, National Tsing Hua University, Hsinchu, Taiwan 65 Department of Physics, Indiana University, Bloomington, Indiana, USA 66a INFN Gruppo Collegato di Udine, Sezione di Trieste, Udine, Italy 66b ICTP, Trieste, Italy 66c Dipartimento Politecnico di Ingegneria e Architettura, Università di Udine, Udine, Italy 67a INFN Sezione di Lecce, Italy 67b Dipartimento di Matematica e Fisica, Università del Salento, Lecce, Italy 68a INFN Sezione di Milano, Italy 68b Dipartimento di Fisica, Università di Milano, Milano, Italy 69a INFN Sezione di Napoli, Italy 69b Dipartimento di Fisica, Università di Napoli, Napoli, Italy 70a INFN Sezione di Pavia, Italy 70b Dipartimento di Fisica, Università di Pavia, Pavia, Italy 052001-17 PHYSICAL REVIEW LETTERS 123, 052001 (2019) 71a INFN Sezione di Pisa, Italy 71b Dipartimento di Fisica E. Fermi, Università di Pisa, Pisa, Italy 72a INFN Sezione di Roma, Italy 72b Dipartimento di Fisica, Sapienza Università di Roma, Roma, Italy 73a INFN Sezione di Roma Tor Vergata, Italy 73b Dipartimento di Fisica, Università di Roma Tor Vergata, Roma, Italy 74a INFN Sezione di Roma Tre, Italy 74b Dipartimento di Matematica e Fisica, Università Roma Tre, Roma, Italy 75a INFN-TIFPA, Italy 75b Università degli Studi di Trento, Trento, Italy 76 Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität, Innsbruck, Austria 77 University of Iowa, Iowa City, Iowa, USA 78 Department of Physics and Astronomy, Iowa State University, Ames, Iowa, USA 79 Joint Institute for Nuclear Research, Dubna, Russia 80a Departamento de Engenharia Elétrica, Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora, Brazil 80b Universidade Federal do Rio De Janeiro COPPE/EE/IF, Rio de Janeiro, Brazil 80c Universidade Federal de São João del Rei (UFSJ), São João del Rei, Brazil 80d Instituto de Física, Universidade de São Paulo, São Paulo, Brazil 81 KEK, High Energy Accelerator Research Organization, Tsukuba, Japan 82 Graduate School of Science, Kobe University, Kobe, Japan 83a AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow, Poland 83b Marian Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland 84 Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland 85 Faculty of Science, Kyoto University, Kyoto, Japan 86 Kyoto University of Education, Kyoto, Japan 87 Research Center for Advanced Particle Physics and Department of Physics, Kyushu University, Fukuoka, Japan 88 Instituto de Física La Plata, Universidad Nacional de La Plata and CONICET, La Plata, Argentina 89 Physics Department, Lancaster University, Lancaster, United Kingdom 90 Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 91 Department of Experimental Particle Physics, Jožef Stefan Institute and Department of Physics, University of Ljubljana, Ljubljana, Slovenia 92 School of Physics and Astronomy, Queen Mary University of London, London, United Kingdom 93 Department of Physics, Royal Holloway University of London, Egham, United Kingdom 94 Department of Physics and Astronomy, University College London, London, United Kingdom 95 Louisiana Tech University, Ruston, Louisiana, USA 96 Fysiska institutionen, Lunds universitet, Lund, Sweden 97 Centre de Calcul de l’Institut National de Physique Nucléaire et de Physique des Particules (IN2P3), Villeurbanne, France 98 Departamento de Física Teorica C-15 and CIAFF, Universidad Autónoma de Madrid, Madrid, Spain 99 Institut für Physik, Universität Mainz, Mainz, Germany 100 School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 101 CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France 102 Department of Physics, University of Massachusetts, Amherst, Massachusetts, USA 103 Department of Physics, McGill University, Montreal, Quebec, Canada 104 School of Physics, University of Melbourne, Victoria, Australia 105 Department of Physics, University of Michigan, Ann Arbor, Michigan, USA 106 Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, USA 107 B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus 108 Research Institute for Nuclear Problems of Byelorussian State University, Minsk, Belarus 109 Group of Particle Physics, University of Montreal, Montreal, Quebec, Canada 110 P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia 111 Institute for Theoretical and Experimental Physics of the National Research Centre Kurchatov Institute, Moscow, Russia 112 National Research Nuclear University MEPhI, Moscow, Russia 113 D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow, Russia 114 Fakultät für Physik, Ludwig-Maximilians-Universität München, München, Germany 115 Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), München, Germany 116 Nagasaki Institute of Applied Science, Nagasaki, Japan 117 Graduate School of Science and Kobayashi-Maskawa Institute, Nagoya University, Nagoya, Japan 118 Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico, USA 119 Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, Netherlands 120 Nikhef National Institute for Subatomic Physics and University of Amsterdam, Amsterdam, Netherlands 052001-18 PHYSICAL REVIEW LETTERS 123, 052001 (2019) 121 Department of Physics, Northern Illinois University, DeKalb, Illinois, USA 122a Budker Institute of Nuclear Physics and NSU, SB RAS, Novosibirsk, Russia 122b Novosibirsk State University Novosibirsk, Russia 123 Institute for High Energy Physics of the National Research Centre Kurchatov Institute, Protvino, Russia 124 Department of Physics, New York University, New York, New York, USA 125 Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo, Japan 126 The Ohio State University, Columbus, Ohio, USA 127 Faculty of Science, Okayama University, Okayama, Japan 128 Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma, USA 129 Department of Physics, Oklahoma State University, Stillwater, Oklahoma, USA 130 Palacký University, RCPTM, Joint Laboratory of Optics, Olomouc, Czech Republic 131 Center for High Energy Physics, University of Oregon, Eugene, Oregon, USA 132 LAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France 133 Graduate School of Science, Osaka University, Osaka, Japan 134 Department of Physics, University of Oslo, Oslo, Norway 135 Department of Physics, Oxford University, Oxford, United Kingdom 136 LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France 137 Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania, USA 138 Konstantinov Nuclear Physics Institute of National Research Centre “Kurchatov Institute”, PNPI, St. Petersburg, Russia 139 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania, USA 140a Laboratório de Instrumentação e Física Experimental de Partículas—LIP, Portugal 140b Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal 140c Departamento de Física, Universidade de Coimbra, Coimbra, Portugal 140d Centro de Física Nuclear da Universidade de Lisboa, Lisboa, Portugal 140e Departamento de Física, Universidade do Minho, Braga, Portugal 140f Universidad de Granada, Granada (Spain), Spain 140g Dep Física and CEFITEC of Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal 141 Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic 142 Czech Technical University in Prague, Prague, Czech Republic 143 Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic 144 Particle Physics Department, Rutherford Appleton Laboratory, Didcot, United Kingdom 145 IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, France 146 Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, California, USA 147a Departamento de Física, Pontificia Universidad Católica de Chile, Santiago, Chile 147b Departamento de Física, Universidad Técnica Federico Santa María, Valparaíso, Chile 148 Department of Physics, University of Washington, Seattle, Washington, USA 149 Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom 150 Department of Physics, Shinshu University, Nagano, Japan 151 Department Physik, Universität Siegen, Siegen, Germany 152 Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada 153 SLAC National Accelerator Laboratory, Stanford, California, USA 154 Physics Department, Royal Institute of Technology, Stockholm, Sweden 155 Departments of Physics and Astronomy, Stony Brook University, Stony Brook, New York, USA 156 Department of Physics and Astronomy, University of Sussex, Brighton, United Kingdom 157 School of Physics, University of Sydney, Sydney, Australia 158 Institute of Physics, Academia Sinica, Taipei, Taiwan 159a E. Andronikashvili Institute of Physics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia 159b High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia 160 Department of Physics, Technion, Israel Institute of Technology, Haifa, Israel 161 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel 162 Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece 163 International Center for Elementary Particle Physics and Department of Physics, University of Tokyo, Tokyo, Japan 164 Graduate School of Science and Technology, Tokyo Metropolitan University, Tokyo, Japan 165 Department of Physics, Tokyo Institute of Technology, Tokyo, Japan 166 Tomsk State University, Tomsk, Russia 167 Department of Physics, University of Toronto, Toronto, Ontario, Canada 168a TRIUMF, Vancouver, British Columbia, Canada 168b Department of Physics and Astronomy, York University, Toronto, Ontario, Canada 169 Division of Physics and Tomonaga Center for the History of the Universe, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan 052001-19 PHYSICAL REVIEW LETTERS 123, 052001 (2019) 170 Department of Physics and Astronomy, Tufts University, Medford, Massachusetts, USA 171 Department of Physics and Astronomy, University of California Irvine, Irvine, California, USA 172 Department of Physics and Astronomy, University of Uppsala, Uppsala, Sweden 173 Department of Physics, University of Illinois, Urbana, Illinois, USA 174 Instituto de Física Corpuscular (IFIC), Centro Mixto Universidad de Valencia—CSIC, Valencia, Spain 175 Department of Physics, University of British Columbia, Vancouver, British Columbia, Canada 176 Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada 177 Fakultät für Physik und Astronomie, Julius-Maximilians-Universität Würzburg, Würzburg, Germany 178 Department of Physics, University of Warwick, Coventry, United Kingdom 179 Waseda University, Tokyo, Japan 180 Department of Particle Physics, Weizmann Institute of Science, Rehovot, Israel 181 Department of Physics, University of Wisconsin, Madison, Wisconsin, USA 182 Fakultät für Mathematik und Naturwissenschaften, Fachgruppe Physik, Bergische Universität Wuppertal, Wuppertal, Germany 183 Department of Physics, Yale University, New Haven, Connecticut, USA 184 Yerevan Physics Institute, Yerevan, Armenia a Deceased. b Also at Department of Physics, King’s College London, London, United Kingdom. c Also at Istanbul University, Department of Physics, Istanbul, Turkey. d Also at Instituto de Fisica Teorica, IFT-UAM/CSIC, Madrid, Spain. e Also at TRIUMF, Vancouver, British Columbia, Canada. f Also at Department of Physics and Astronomy, University of Louisville, Louisville, Kentucky, USA. g Also at Physics Department, An-Najah National University, Nablus, Palestine. h Also at Department of Physics, California State University, Fresno, USA. i Also at Department of Physics, University of Fribourg, Fribourg, Switzerland. j Also at Physics Dept, University of South Africa, Pretoria, South Africa. k Also at Departament de Fisica de la Universitat Autonoma de Barcelona, Barcelona, Spain. l Also at Tomsk State University, Tomsk, and Moscow Institute of Physics and Technology State University, Dolgoprudny, Russia. m Also at The Collaborative Innovation Center of Quantum Matter (CICQM), Beijing, China. n Also at Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal. o Also at Universita di Napoli Parthenope, Napoli, Italy. p Also at Institute of Particle Physics (IPP), Canada. q Also at Department of Physics, University of Adelaide, Adelaide, Australia. r Also at Department of Physics, St. Petersburg State Polytechnical University, St. Petersburg, Russia. s Also at Department of Financial and Management Engineering, University of the Aegean, Chios, Greece. t Also at Centre for High Performance Computing, CSIR Campus, Rosebank, Cape Town, South Africa. u Also at Department of Physics, California State University, East Bay, USA. v Also at Institucio Catalana de Recerca i Estudis Avancats, ICREA, Barcelona, Spain. w Also at Department of Physics, University of Michigan, Ann Arbor, Michigan, USA. x Also at LAL, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France. y Also at Graduate School of Science, Osaka University, Osaka, Japan. z Also at Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany. aa Also at Institute of Physics, Azerbaijan Academy of Sciences, Baku, Azerbaijan. bb Also at Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen/Nikhef, Nijmegen, Netherlands. cc Also at Institute of Theoretical Physics, Ilia State University, Tbilisi, Georgia. dd Also at CERN, Geneva, Switzerland. ee Also at Department of Physics, Stanford University, Stanford, California, USA. ff Also at Manhattan College, New York, New York, USA. gg Also at Joint Institute for Nuclear Research, Dubna, Russia. hh Also at Hellenic Open University, Patras, Greece. ii Also at The City College of New York, New York, New York, USA. jj Also at Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China. kk Also at Department of Physics, California State University, Sacramento, USA. ll Also at Moscow Institute of Physics and Technology State University, Dolgoprudny, Russia. mm Also at Département de Physique Nucléaire et Corpusculaire, Université de Genève, Genève, Switzerland. nn Also at Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom. oo Also at Louisiana Tech University, Ruston, Louisiana, USA. pp Also at School of Physics, Sun Yat-sen University, Guangzhou, China. qq Also at Institute for Nuclear Research and Nuclear Energy (INRNE) of the Bulgarian Academy of Sciences, Sofia, Bulgaria. 052001-20 PHYSICAL REVIEW LETTERS 123, 052001 (2019) rr Also at Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia. ss Also at Department of Applied Physics and Astronomy, University of Sharjah, Sharjah, United Arab Emirates. tt Also at Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany. uu Also at CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France. vv Also at National Research Nuclear University MEPhI, Moscow, Russia. ww Also at Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics, Budapest, Hungary. xx Also at Giresun University, Faculty of Engineering, Giresun, Turkey. yy Also at Institute of Physics, Academia Sinica, Taipei, Taiwan. zz Also at LPNHE, Sorbonne Université, Paris Diderot Sorbonne Paris Cité, CNRS/IN2P3, Paris, France. aaa Also at Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, USA. 052001-21